1. Field of the Invention
Embodiments of the present invention relate to the field of video digital-to-analog converters. More particularly, embodiments of the present invention relate generally to the detection of an external load on a video digital-to-analog converter.
2. Related Art
Digital video electronic devices (e.g., digital video disk (DVD) players) are designed to output video signals in various analog formats. In this way, various analog video displays are able to present the output video signals using any one of the supported analog formats.
For example, a video electronic device may support the following analog video formats: composite video burst sync (CVBS) signals, S-video signals, and YUV signals, etc. Each of the analog video formats comprises one or more connections that are used for viewing the video signal. For example, one connection is required for CVBS signals, two connections are required for S-video signals, and 3 connections are required for YUV or RGB signals. Display devices (e.g., television) are coupled to the connections to view the video signals in the various formats.
A video digital-to-analog converter (DAC) is coupled to each of the connections that support the various analog video formats. As such, for a video electronic device supporting CVBS, S-video and YUV (or RGB) video signals, six DACs are required to support six connections. Typically, only one format is selected by a user to view the output video signal.
However, in conventional digital video electronic devices all the supporting DACs provide video signals on a continual basis in order to support the various formats. As such, in the video electronic device that supports CVBS, S-video and YUV video signals, all six DACs output video signals, even if only one connection (e.g., CVBS) is used. For those output video signals that are unused, a significant waste of energy is presented. This may become problematic especially, when power is a critical issue, such as, in portable devices.
Conventional systems and methods test for external loads (e.g., display devices) that are coupled to the connectors. In this way, those connectors that are not coupled to external loads can be disabled in an effort to save wasted power. However, these conventional systems and methods rely on generating special test signals used for detecting the presence of an external load. This requires additional circuitry on devices where space may be critical. Also, conventional systems and methods only test for the external load during a small window that is presented in the video output signal. As a result, the conventional systems and methods are complex and prone to latency while waiting for the window of opportunity in the video output signal.
As such, there is a need for a video DAC that is capable of detecting external loads without generating any special test signals, and that is capable of testing for an external load without testing for the external load during a small window in the video output signal.